= form_for(@line_item) do |f| 
  - if @line_item.errors.any? 
    #error_explanation
      %h2= "#{pluralize(@line_item.errors.count, "error")} prohibited this line_item from being saved:"

      %ul
        - @line_item.errors.full_messages.each do |msg|
          %li= msg 
      
   

  .field
    = f.label :product
    = f.text_field :product
  .field
    = f.label :cart
    = f.text_field :cart
  .actions
    = f.submit 'Save'